Trepan with automatic stop means



June 2, 1970 A. KELLER 3,515,100

TREPAN WITH AUTOMATIC STOP MEANS Filed June 27, 1967 Fig. 3

Fig. 1

Unite St t s P tent 015cc 3,515,100 Patented June 2, 1970 3 515,100 TREPAN WITH AUTOMATIC STOP MEANS Arnold Keller, Kiel-Dietrichsdorf, Germany, assignor to Austenal Europa, Inc., Kiel-Dietrichs'dorf, Germany Filed June 27, 1967, Ser. No. 649,343 Claims priority, application Germany, July 4, 1966,

Int. Cl. A61b 17/ 16; B23b 47/32 US. Cl. 128-310 2 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF INVENTION The invention relates to a skull bone drill or a trepan comprising a drill, the depthof penetration of which may be limited by a stop.

The known trepans are not quite satisfactory inasmuch as the use thereof makes the availability of certain auxiliaries a prerequisite. The opening of. the skull bone, namely, is very dangerous without these special auxiliary means-because there is the danger that when boring a hole into the skull bone, the unsupported drill may under certain circumstances penetrate into the interior of the skull so deeply that the dura and possibly even the brain may be hurt. With, the known trepans, a point arranged laterally of the drill is generally provided as a support for the trepan during the drilling operation. This is subject to the disadvantage that after termination of the drilling operation the drill of the instrument may yet still penetrate farther into the borehole and thus into the skull.

sUMMAR Y OF INVENTION depth of the hole already drilled. I

The trepan according to the invention comprises a housing, a driving shaft rotatably supported in said hous ing and connected to rotational drivemean's', an'out'put shaft rotatably supported in said housing and provided bined with a backward movement of said supporting plate with respect to said drill.

Moreover, the trepan provided with said spindle is characterized in that said spindle is provided with a second coupling, subjected to the force of second resilient means, a half of said second coupling being fastened to the spindle gear and the other half being fastened to said spindle or a member fastened thereto, whereby the spindle carrying the supporting plate is moved back with respect to the drill only if the drilling pressure acts onto the supporting plate and forces said second coupling into engagement againstthe action of said second resilient means.

Other features of the trepan according to the invention will be understood from the following detailed description of the drawing showing an illustrative embodiment.

BRIEF DESCRIPTION OF THE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENT The trepan comprises a housing 1 with a driving shaft 2 supported in an antifriction bearing 3 and provided at its front end 'with a coupling half 4 which may be engaged with a coupling half 7 biased by a spring 6. The driving shaft 2 is connected to rotational drive means (not shown).

The coupling half 7 is arranged at one end of an output shaft 8 with a gear 9 and a drill chuck .11 provided at the other end. A drill 12 tapered towards its tang 13 may be inserted into the drill chuck 11 and is replaceably retained therein by means of a set screw 14.

The gear 9 arranged on the output shaft '8 meshes with another gear 16 which is arranged around a spindle 18 subjected to the tension of a spring 17. The gear 16 is provided with a coupling half 19 at its front end face, said coupling half being in cooperation with another coupling half 21 arranged on the front end portion of the spindle 18 which comprises a regulator'wheel 23 and a supporting plate 26 at its front end facing away from the coupling half 21, said supporting plate being provided with centerat the front end thereof with a drill chuck which retains a drill projecting from said housing, a first coupling ar ranged between said output shaft and said driving shaft and adapted to transmit rotational movement from the driving shaft to the output shaft, said first coupling being forced permanently out of engagement by first resilient means and adapted to be forced into engagement against the force of said first resilient means by the action of the drill pressure, and supporting means connected to said housing adjacent said drill and adapted to limit the depth of penetration of the drill into the skull bone.

Another feature of the invention consists in that the supporting means comprise a spindle rotatably supported in said housing and provided with a supporting plate at the front end thereof, said spindle having arranged a gear thereon which is in mesh with another gear arranged on the output shaft, whereby the rotation of the drill is coming pins 24 and a center bore 22 for the movement of the drill 12. In the shown embodiment the coupling half 21 is arranged at the rear side of the regulator wheel.

I A guiding pin 27 projecting from the back side of the, supporting plate 26 is guided in a recess not designated with a'reference numeral,..and provided in a housing portion 28 containing the gear 16, the coupling halves 19 and 21 as well as the spindle 18 and the wheel 23. To be able to rotate the wheel, the housing portion 28 is provided with'a corresponding aperture 2 9.

The operation of the trepan inaccordance with the invention is as follows:

The coupling 4, 7 provided between the driving shaft 2 and the output shaft 8 and biased by a spring 6 is in engagement and transmits rotational movement to the drill 12 to perform a drilling operation only if a drilling pressure is exerted against the cutters or the bit. Immediately the drill bit or the drill cutters, respectively, have penetrated the skull bone and thus the drilling pressure has ceased, the coupling half 7 is separated from the coupling half 4 on effect of the spring 6, so that further drive of the drill 12 is prevented. In order to avoid any further penetration of the drill into the interior of the skull, the supporting plate 26 is provided. The latter is adjusted prior to starting the drilling operation by means of the regulator wheel 23 and the spindle 18, in such a manner that it is 3 approximately aligned with the drill bit. If now the drilling operation is started,the gears 9 and '16 being inmesh with each other are effective in such a manner that with increasing penetration of the drill into the skullbone the supporting plate 2-6 is uniformly moved back against the force of the spring 17.

The supporting plate 26 is thus moved backupon a rotary movement of the drill, that means this movement is taking place only if the drill 12 is driven via the coupling 4, 7. The gears 9 and 16 thus have the function of slacking back the supporting plate 26 as long as the drilling pressure lasts, i.e. as long as the drill 12 is penetrating into the skull home. It does not matter in this connection how thick the skull bone is because I the automatic slacking back or leading back of the supporting plate 26 at any rate takes place only until the drilling pressure ceases, i.e. until the drill 12 has just penetrated the skull bone. Thereupon, namely, the coupling 4, 7 will disengage and the output shaft 8 with the drill 12 will stop and thus also the meshing gears 9 and 16 will come to a standstill. p

In order to prevent the supporting plate 26 from being slackened back more quickly than the drill 12 penetrates into the skull bone, coupling half 19 is arranged at the gear 16, said coupling half cooperating with the coupling half 21 fastened to the spindle 18 or a member fixed thereto, e.g. the regulator wheel. This coupling 19, 21 is effective to rotate the spindle 18 in order to lift the supporting plate 26 with respect to the drill only if the supporting plate 26 with its centering pins 24 actually is in contact with the skull bone and the drilling pressure acts upon said plate.

The technical progress obtained with the trepan in accordance with the invention is substantial. A simple and handy surgical instrument has been provided which combines all the mechanical parts necessary to perform its function in one single housing, which is important especially with respect to the necessity of keeping the instruments sterile. Moreover, the drill chuck 11 allows for an easy replacement of the drills simply by loosening the set screw 14 so that a borehole of desired diameter may be obtained at any time without any efforts.

In order to prepare the instrument for operation it is only necessary to bring the supporting plate 26 in position prior to the beginning of the boring operation, This can be done by simple right-handturning the regulator wheel 23 to a stop not designated in more detail, at which the supporting plate being approximately aligned with the drill bit. It is therefore not necessary to, adjust pre-. viously any dimensions 'be it by feeling or measuring or the like preparations.

Finally, the considerable tapering of the drill 12 from the bit to the tang thereof guarantees that jamming of the drill is prevented which may easily occur in the case of cylindrically designed drills, especially if the cutters have become blunt. A jamming of the drill in the bore hole is dangerous insofar as thereby the spring force of the coupling 4, 7 might become insufficient to disengage the latter although the drill has pentrated the skull bone.

What I claim is:

1. An automatic trepan comprising, in combination, a

'ing,first coupling means defined on said shaft connectible' 4 housing, a driving shaft rotatably supported in said housto rotational drive means, first clutch means mounted on said shaft, an output shaft axially aligned with said driving shaft rotatably and axially shiftably supported in said housing having an end projecting from said housing, a drill chuck afiixed to said projecting end for interchangeably receiving an retaining drilling tools, second clutch means defined on said output shaft in opposed relation to said first clutch means, first spring means biasing said output shaft in a direction separating said first and second clutch means whereby axial force on said output shaft during drilling overcomes said spring means to engage said first and second clutch means, a threaded spindle arranged in parallel spaced relation to said output shaft mounted in said housing and axially shiftable thereto having an end projecting out of said housing and adjacently disposed to said output shaft projecting end, second spring means biasing said spindle in the direction of its projecting end, a drive gear rigidly secured to said output shaft meshing with an idler gear rotatably supported on said threaded spindle, a manually operable adjustment nut arranged on said threaded spindle adjacent said idler gear for axially positioning said spindle, normally disengaged second coupling means arranged between said idler gear and said adjustment nut engageable upon said threaded spindle being axially shifted against the biasing force of said second spring means, a supporting plate secured to said projecting end of said threaded .spindle having an aperture through which a drill tool extends, said supporting plate engaging the surrounding skull zone of the drill tool thereby preventing tilting of the trepan during and after the drilling operation and at the end thereof, a guide pin affixed to said supporting plate in diametrically opposed relation to. said threaded spindle with respect to said aperture, and a recess formed in said housing slidably receiving said guide pin.

. 2. .A trepan as defined in clairn 1, wherein an access opening to said adjustment nut is defined in the wall of said housing.

References Cited UNITED STATES PATENTS 2,401,548 6/1946 Chapman 128 310' 2,504,075 '4/1950 'Ka'rle 128-319 2,525,669 10/1950 Hainault, 128-3 10 2,675,003 4/1954 Veley 128 310 2,299,267 10/1942 Fisher.

2,842,131 7/1958 Smith 128'3l0 2,967,441 1/19 1 Miles 77-55 I FOREIGN PATENTS" 201,371 8/1923 GreatBritain.

ANTON O. OECI- ISLE, Primary Examiner v R. J. APLEY, Assistant Examiner I us. 01. X.R. 

